Process for coating aggregate with bituminous binder



XR 297609878 tX o l n Umted States l atent O PROCESS FOR COATINGAGGREGATE WITH BITUMINOUS BINDER Marcel Louis Lhorty, Rouen, France,assignor to Shell Development Company, Emeryville, Calif., a corporationof Delaware No Drawing. Application July 15, 1953, Serial No. 368,212Claims priority, application France July 22, 1952 19 Claims.(Cl.106-269) This invention relates to a process for the coating ofaggregates. More particularly, it is concerned with the coating ofmixed'a'ggregates with bituminous materials.

In the preparation of paving compositions it is normal practice to mixbituminous materials, such as asphalt, with aggregates of various sizesdepending upon the end use. The efiiciency with which the bituminousmaterial coats the aggregate is related to a number of properties suchas the source and history of the binder material, the acidic or basiccharacter of the aggregate, and the size of the aggregate particles.Various treatments and processes as well as additives have been employedfor the purpose of increasing the adhesion of the binder to theaggregate. For the most part, the additives which are most successfulmay be described as those surface active agents bearing at least onelipophilic radical per molecule. It is believed that regardless of themethod of application at least part of the additive migrates to theinterface between the aggregate and the binder. The lipophilic radicalsof the surface active agent provide the aggregate surface with anoleophilic coating, whereupon the binder is more strongly bound to theaggregate. This process for improving such compositions is onlyeffective, of course, as long as each of the aggregate particles issubstantially uniformly coated with an oleophilic surface active agent.

As long as the aggregate is relatively uniform in particle size thesurfactant may be applied by several methods. It may, for example, bedispersed in the asphalt which is then mixed with the aggregate.Alternatively, the aggregate is primed with a dispersion of the surfaceactive agent following which the binder is mixed with the primedaggregate. Combinations of these two processes also have been employed.However, these methods have not been successful for the adequate coatingof the aggregates containing particles of widely differing surfaceareas. If, for example, the aggregate mixture contains a substantialproportion of fine particles such as fine sand, it has been found thatboth the primer and the bituminous binder are selectively attracted tothe relatively finer aggregate particles, while the coarser particlesremain unprimed and uncoated. Under these conditions a pavement such asa road commences to disintegrate within a short period of time, theuncoated coarse particles falling away as gravel. One possible means forovercoming this disadvantage would be to fractionate the aggregate intocoarse and fine fractions, coating each fraction separately with thebinder and then combining the several coated fractions. It is obviousthat such an expedient is uneconomical.

It is an object of the present invention to improve the process forcoating aggregates with bituminous binders. It is another object of thisinvention to improve the process for coating aggregates containing asubstantial proportion of fine particles with asphaltic materials. It isa particular object of this invention to improve the process for coatingmixed aggregates so as to provide both coarse and fine particles with asubstantially uniform coating of a bituminous binder. Other objects willbecome apparent during the following discussion.

Now in accordance with the present invention, a means has been found forthe uniform coating of mixed aggre- 2,760,878 Patented Aug. 28, 1956gates wherein the aggregate contains both relatively fine aggregateparticles and relatively coarse particles. The process comprises primingthe aggregate with a surface active agent having at least one lipophilicradical as a portion of each molecule thereof, whereby the relativelyfine aggregate particles are preferentially coated with the primer,mixing the partially primed aggregate with a bituminous binder wherebythe binder is attracted to and coats the primed aggregate particleswhile the relatively coarse particles remain substantially unaltered;applying a second portion of the same or different surface active agent,which primes the relatively unaffected coarser aggregate particles andcontinuing the mixing whereby all of the aggregate, both fine and coarseparticles, become substantially uniformly coated with the asphalticbinding.

The use of this invention enables the satisfactory preparation ofasphaltic paving compositions wherein the aggregate employed contains asubstantial proportion of fine particles, that is, particles having amaximum diameter of 5 millimeters or less. The process is particularlyapplicable to mixed mineral aggregates containing from about 5% to about60% by weight of such fine particles (usually having minimum diametersof about 0.5 mm.) and especially where the aggregate contains at least10% of the fine aggregate. Under such conditions it is preferred thatthe initial priming of the aggregate be accomplished with from about 25%to about by weight of the total surface active agent employed in thecomposition.

The priming may be accomplished with any of the known varieties ofsurface active agents which contain at least one lipophilic radical permolecule. In general, these comprise anionic substances such as organicacids (oleic acid, stearic acid, and other fatty acids having 12-24carbon atoms per molecule), soaps, preferably those of polyvalent metalswith fatty acids (aluminum stearate, zinc oleate, etc.), and cationicmaterials. The latter class are the most widely used and are preferred.

For the most part, the cationic materials comprise organic nitrogenousbases, although other onium compounds may be employed such asphosphonium, iodonium, stibonium, arsonium and the like.

Suitable substances to be used as the amino compound are the organiccompounds containing an amino group and a. lipophilic radical in themolecule, as well as derivatives of such compounds. A preferred group ofamino compounds consists of products containing a radical derived fromthe fatty glycerides such as vegetable oils. Such amino compounds can,for instance, be obtained by condensation of ammonia with a fattysubstance of vegetable origin to form nitriles which are then hydrolyzedto amines.

The amino compounds containing a radical derived from a fatty substancemay be the soaps of a monoamine or a polyamine of a higher fatty acidhaving at least 12 carbon atoms, and probably 16-20 carbon atoms permolecule. Suitable acids are variously derived from vegetable and animaloils such as oleic acid, linoleic acid, and stearic acid, as well astheir homologs and analogs.

The acyl amides derived from a higher fatty acid as well as the acylamido amines derived from a higher fatty acids are also suitable. Theacyl amido amines can be obtained by reacting a polyamine with an acidwhile converting at least one of the amino groups of the polyamine intothe acyl amide structure and leaving at least one other of the aminogroups in a free state. The soaps of the acyl amido amines obtained byreacting at least one of the free amino groups of the acyl amido aminewith an organic or inorganic acid may also be used.

The soaps of an amine, the acyl amides, and the acyl amido aminesreferred to above can also be derived from organic acids of highmolecular weight other than the higher fatty acids. Preferred varietiesof alternative materials comprise those obtained from the naphthenieacid fractions derived from petroleum oil as well as such other naturaloccurring materials as tall oil and the like- Examples of polyamineswhich may be used as initial material for obtaining the above mentionedderivatives of the organic acids are preferably alkylene polyamines andpolyalkylene polyamines including ethylene diamine, propylene diamine,diethylene triamine, triethylene tetram-ine, tetraethylene pentamine,and hexamethylene diamine. A preferred group of polyamines comprises thematerials obtained by hydrogenation of the condensation products ofacr-olein or of epoxides such as epichlorohydrin with ammonia or withlower molecular weight primary or secondary amines. Preferably thelipophilic character of 'such materials is enhanced by reaction of thecondensation product with less than an equivalent amount of anoleophilic organic acid such as the higher fatty acids including thosereferred to hereinbefore.

\Another class of amino compounds suitable for the purpose of thepresent invention consists of higher alkyl amines and alkenylamineshaving at least 12 carbon atoms and preferably 16-20 carbon atoms permolecule. These include species such as hexadecyl amine, heptadecylamine, octadecyl amine, and octadecenylamine as well as the polyalkylenepolyamines containing more than 8 carbon atoms. Other suitable aminesare those bearing cyclic hydrocarbon radicals such as abietylamine andnaphthenylamine.

In order to enhance the adhesion characteristics promoted by thesematerials it is preferred, but not essential, that they be combined inthe present process with an inorganic salt of a polyvalent metal. Thepolyvalent metal is preferably an amphoteric metal, such substances aszinc, tin, iron, lead, and chromium being preferred. Especially when theaggregate is primed with an aqueous dispersion of these materials it ispreferred that the latter also include an inorganic acid, especially themineral acids such as sulfuric, nitric, hydrochloric, hydrobromic, orphosphoric acids. The inorganic salts are preferably those of the sametype of acids, although mixtures of either acids or salts or both may beemployed.

While the priming materials may be added directly to the aggregatewithout substantial modification, it is preferred for economic andtechnical reasons to disperse them either in solution or morepreferably, in an aqueous emulsion. In the latter case, an oil-in-wateremulsion is preferred. When employing a priming composition comprisingan aqueous emulsion, a polyvalent metal salt and an inorganic acid aredispersed in the aqueous phase, the oleophilic surface active agentbeing substantially dispersed in the oil phase of the emulsion. Undersome circumstances, when salts are formed between the inorganic acid anda surface active amino compound, the salt may be dispersed in bothphases.

The oil phase of such emulsions is preferably a mineral oil of heavycharacter such as road oil, or fuel oil. The mineral oil may also be amixture of a heavy oil and a lighter oil, such as the mixture of roadoil and kerosene. In the latter instance, a mixture of 50-80% road oilwith 20-50% kerosene is satisfactory. It is also possible to use anaromatic extract obtained by the extraction of a mineral oil by means ofa selective solvent. The mineral oil phase may constitute from about 1%to about 50% by weight of the total priming emulsion. It is preferredthat the amine be present in an amount between about 3% and about 30% byweight of the priming emulsion. Any water soluble polyvalent metal saltwhich is present should be employed in amounts less than about by weightof the emulsion. If an inorganic acid is employed, it should be utilizedin amounts between about 0.5% and about 10%, based on the total weightof the emulsion. It will 'be understood that this proportion of acid maybe distributed between free inorganic acid and any that is combined insalt form with the amino compound. In order to be effective for thepresent purpose suficient priming composition is employed in thecomhined priming operations so that from about 0.001% to about 0.1% ofthe surface active agent based on the aggregate is deposited on thesurface thereof.

After the initial priming operation, when the relatively fine aggregateparticles are primed, the asphaltic binder is mixed therewith usually inamounts between about 0.5% and about 10% by weight of the aggregate andbased upon the relatively non-volatile portions of the bindercomposition. For the purpose of application and convenience in handling,the binder may be dispersed as an aqueous emulsion or may be used in theform of a cut back or solution.

Under the preferred conditions, and when the mineral aggregate containsfrom about 10% to about 60% of particles having maximum diameters lessthan 5 millimeters, the first priming operation is effected with the useof between about 40% and about 65% by weigh-t of the total surfaceactive agents. Under such circumstances, when employing an emulsion forthe purpose of priming the emulsion should contain between about 0.1%and about 1% by weight of the emulsion of amphoteric metal inorganicsalt and between about 1% and about 6% by weight of the emulsion of themineral acid. The emulsion should also contain from about 10% to about20% based on the weight of the emulsion of the hydrophobic surfaceactive agent and depositing on the aggregate between about 0.005% andabout 0.03% based on the weight of the aggregate of the surface activeagent. Under such circumstances it is preferred that the binder beemployed in amounts between about 3% and about 7% based on the weight ofthe aggregate.

The aqueous suspension can be prepared by intimately mixing the oil andthe amino compound with an aqueous solution of the water-solubleinorganic salt of a polyvalent metal at a temperature of 70-80 C. Anemulsion of water in the oil phase is formed. The acid used, such asstrong inorganic acid, is slowly added to this emulsion. By adding theacid, the emulsion is reversed whereby the desired emulsion of oil inthe aqueous phase is obtained. When it is desired to prepare and use anaqueous suspension containing no inorganic salt the preparation of thesuspension can be carried out in a similar way.

Preferably, all the operations for preparing the aqueous emulsions arecarried out at temperatures not exceeding about C. The aggregate may bepre-coated with the emulsion or other composition containing theoleophilic surface active agent by spraying or by wetting the aggregatein any manner. It is advantageous to atomize the aqueous suspension onthe surface of the aggregates. The priming may be carried out in amixing or crushing plant, especially when the crushed aggregate istransported on a conveyor belt, in such a way as to permit theinstallation of a spraying device about the belt. In particular, thistechnique may be employed in the case of pre-treatment or priming offine gravel intended for surface spreading. Wetting the aggregate withthe emulsion of the primer can be done during loading of the graveltrucks at the moment when the aggregate is being transported on theconveyor belt leading from the shovelling device to the trucks.

After the initial application of the desired portion of the primingsolution the bituminous binder may be applied to the aggregate in anyknown manner. The priming of the aggregate with the suspension makes itpossible to coat the relatively fine particles thereof with thebituminous binder in an effective manner, but leaves the relativelycoarser particles in substantially their original condition.

Bituminous binders which may be employed include residual asphalts,pyrogenous asphalts, blown asphalts, and natural asphalts orasphaltites.

Having effectively coated the relatively finer aggregate particles, theremaining portion of the oleophilic surface active agent is applied withagitation whereupon the relatively coarser aggregate particles areprimed therewith. Upon continued agitation of the entire mixture theasphaltic binder is relatively uniformly distributed on all of theaggregate particles regardless of their relative size or surface area.

One of the advantages gained by the use of the present process, inaddition to the relatively uniform coating of all of the aggregateparticles, Comprises the substantial reduction in the minimumrequirement for surface active agent in order to promote satisfactoryadhesion of the asphalt or other bituminous substance to the aggregate.

The example which follows describes a typical embodiment of the presentinvention: 1430 kilograms of water were introduced into a mixer andheated to 60 C. Aluminum sulfate, crushed to nut size, was added anddissolved in the water. The temperature was raised to about 70 C. afterwhich 240 kilograms of hydrocarbon oil comprising 25% by weight of fueloil and 75% by weight of aromatic extract obtained from lubricating oilfractionation were dispersed in the water. Following this, a mixture offatty amines predominating in octadecyl amine were introduced so as toprovide the emulsion with an amine concentration of approximately 5%.Hydrochloric acid was finally added in an amount of about 2% based onthe weight of the total emulsion.

When this emulsion is added in a single step to aggregate comprisingapproximately 35% by weight of particles having diameters less than 5millimeters, the priming is not satisfactory since it adheres largely tothe finer particles while the relatively coarser material is not primed.Consequently, when asphalt is added thereto an incomplete coating of theaggregate occurs and the resulting composition exhibits poor weatheringproperties. In overcoming these difiiculties the present invention isemployed by using two substantially equal applications of theabovedescribed priming emulsion and applying the asphalt binder betweenthe primer applications. The resulting composition is found to havesubstantially uniform coating of the binder throughout the aggregateparticles regardless of their relative size and the composition exhibitsgreatly improved weathering properties.

A preferred process for preparing priming emulsions having superiorproperties with respect to increasing the adhesion of later appliedbituminous coatings comprises dispersing the adhesion agent i. e., anamine, an an aqueous medium, comprising either water or a water solutionof an inorganic polyvalent metal salt, following which an inorganicacid, such as hydrochloric acid, and mineral oil are added. For somereason as yet undetermined, it has been found that emulsions so formedexhibit at least about 20% additional adhesion improvement as comparedwith emulsions prepared by other means. For example, if the emulsionsare prepared by mixing oil and the amino compound with an aqueoussolution of the polyvalent metal salt, a water-in-oil emulsion is formedfollowing which acid is added in order to cause inversion of theemulsion. However, it has been determined that such emulsions,

while satisfactory for most purposes, are only about as effective asprimers as compared with emulsions prepared by the above preferredprocess.

The examples which follow illustrate the advantages gained by the use ofthe present invention:

EXAMPLE 1 An emulsion having the following composition was used forpriming a quartzite having aggregate particles whose maximum diametersvary from about 1 mm. to 20 mm.

Parts by weight Water 71.5 Aluminum sulfate (calc. anhyd.) 1 Fuel oil 12CisCis fatty amines 12 Hydrochloric acid (density 1.19) 3.5

6% by weight based on the aggregate of an asphalt cut back was used tocoat the quartzite.

Table l, which follows, shows comparative data proving that (1) lessprimer is required when using multiple addition and (2) adhesion valuesare increased by multiple addition, even if the total quantity of primeris less than that used in a single addition. Test 3 shows that furtherbenefits result from atomizing the primer instead of employing ordinaryspray.

Table I.Laborat0ry tests carried out with quartzite 0/20 EXAMPLE II Asecond set of comparative tests were made, utilizing a porphyryaggregate having a wide particle size distribution and a primingemulsion as follows:

Parts by weight Water 62.5 Aluminum sulfate 2.5 Road oil l0 Kerosene 5C1s1s fatty amines 15 Hydrocholric acid 5 Table II below shows that theadvantage of multiple addition for the treatment of this type ofaggregate is especially beneficial.

Table II.Tests carried out in a concrete mixer with corbigny porphyryTest 1 Test 2 Test 3 Test 4 Temperature 14 C 14 C 12 C 12 0. Weight ofgravel per mix kg 90 kg 90 kg 90 kg. Water content of gravel 5% 5%.-- 5%5%. Percent of asphalt cutback calc. on 6%. 6% 6% 6%.

aggregate. Term. of binder 90100 C 90-100 C 90-100 C 90-100 C. Primingemulsion:

Total quantity used calc. on 2 kg./ton 3 kg./ton 1.5 kg./ton.

aggregate. Concentrated emulsion diluted 15% 20% 15%.

0. Time of use before coating before coating, 50% before coating, 50%before coating, is after coating. 50% after coating. 50% after coating.Percent of surface of gravel coated. 20% "A 90%. Destruction of coatingupon negligible negligible negligible negligible.

immediate immersion.

I claim as my invention:

1. The method of coating mineral aggregate containing both fine andcoarse aggregate particles which comprises priming said aggregate with afirst portion of an oil-inwater emulsion, said emulsion comprising anaqueous phase having dissolved therein from about 0.1% and about 1% byweight of the emulsion of a water soluble amphoteric metal inorganicsalt and from about 1% to about 6% by weight based on the emulsion of amineral acid, and a hydrocarbon phase having dissolved therein fromabout 10% to about 20% based on the weight of the emulsion of analiphatic amino compound bearing at least one lipophilic radical permolecule, whereby the fine aggregate particles having maximum diametersless than about mm. are coated with the primer and the coarser particlesare substantially unaffected; mixing with the primed aggregate betweenabout 3% to about 7% by weigh-t, based on the aggregate, of a bituminousbinder, whereby the fine aggregate particles are coated therewith whilethe coarser aggregate particles are substantially uncoated; admixing asecond portion of said priming emulsion, whereby the coarse aggregateparticles are primed therewith; and mixing the entire composition,whereby both fine and coarse aggregate particles are coated with thebinder; the total proportion of amino compound being between about0.005% to about 0.03% based on the weight of the aggregate.

2. A process according to claim 1 wherein the acid is 4 hydrochloricacid.

3. A process according to claim 1 wherein the salt is aluminum sulfate.

4. A process according to claim 1 wherein the amino compound is a higheraliphatic amine.

5. A process according to claim 1 wherein the amino compound is an alkylamine having an alkyl radical of 12-20 carbon atoms.

6. A process according to claim 1 wherein the amino compound is apartial amide of a higher fatty acid and an aliphatic polyamine.

7. A process according to claim 1 wherein the bituminous binder isasphalt.

' a first portion of an aqueous emulsion of an amino compound bearing atleast one lipophilic radical and a watersoluble inorganic salt of apolyvalent metal, whereby the fine aggregate particles arepreferentially primed, but the coarse particles are substantiallyunaffected, applying a bituminous binder, whereby the fine particles arecoated therewith, applying a second portion of said priming emulsion,whereby the coarse particles are primed, and mixing the entirecomposition whereby both the coarse and fine particles are coated withthe binder, the first portion of the priming solution containing fromabout 40% to about 65% by weight of the total amino compound, the totalamount of amino compound utilized being between about 0.001% and about0.1% by weight based on the aggregate.

12. The method of coating mineral aggregate containing both fine andcoarse aggregate particles which comprises priming said aggregate with afirst portion of an oil-in-water emulsion, said emulsion comprising anaqueous phase having dissolved therein from 0.0% to about by weight ofthe emulsion of a water-soluble polyvalent metal salt and between about0.5% and about 10% based on the emulsion of an inorganic acid, and

a hydrocarbon phase having dissolved therein, from about 3% to about 30%by weight of the emulsion of an amino compound bearing at least onelipophilic radical per molecule, whereby the fine aggregate particleshaving maximum diameters less than about 5 mm. are coated with theprimer and the coarser particles are substantially unaffected; mixingwith the primed aggregate between about 0.5% and about 10% by weight,based on the aggregate, of a bituminous binder, whereby the fineaggregate particles are coated therewith; admixing a second portion-ofsaid priming emulsion, whereby the coarse aggregate particles are coatedtherewith; and mixing the entire composition, whereby both fine andcoarse aggregate particles are coated with the binder; the totalproportion of amino compound being between about 0.001% to about 0.1% byweight based on the aggregate.

13. The method of coating mineral aggregate containing both fine andcoarse particles which comprises priming the aggregate with a firstportion of a surface active agent having at least one lipophilic radicalper molecule, whereby the relatively fine aggregate particles arepreferentially primed, applying a bituminous binder, whereby the primedparticles are coated with binder, applying a second portion of a surfaceactive agent to the partially coated aggregate, whereby the uncoatedrelatively coarse aggregated particles are primed, and mixing the entirecomposition, whereby both the coarse and fine aggregate particles becomecoated with the bituminous binder, said surface active agent being ananionic material the total amount of said surface-active agent beingbetween about 0.001% and about 0.1% by weight based on the aggregate.

14. The method of coating mineral aggregate containing both fine andcoarse particles which comprises priming the aggregate with a firstportion of a surface active agent having at least one lipophilic radicalper molecule, whereby the relatively fine aggregate particles arepreferentially primed, applying a bituminous binder, whereby the primedparticles are coated with binder, applying a second portion of a surfaceactive agent to the partially coated aggregate, whereby the uncoatedrelatively coarse aggregated particles are primed, and mixing the entirecomposition, whereby the coarse and fine aggregate particles becomecoated with the bituminous binder, said surface active agent being acationic material the total amount of said surface-active agent beingbetween about 0.001% and about 0.1% by weight based on the aggregate.

15. The method of coating mineral aggregate containing both fine andcoarse aggregate particles which comprises priming the aggregate with afirst portion of a surface active agent having at least one lipophilicradical per molecule, whereby the relatively fine aggregate particlesare preferentially primed, applying a bituminous binder, whereby theprimed particles are coated with binder, applying a second portion of asurface active agent to the partially coated aggregate, whereby theuncoated relatively coarse aggregated particles are primed, and mixingthe entire composition, whereby the coarse and fine aggregate particlesbecome coated with the bitumi nous binder, said surface active agentbeing applied in the form of a solution the total amount of saidsurfaceactive agent being between about 0.001% and about 0.1% by weightbased on the aggregate.

16. The method of coating mineral aggregate containing both fine andcoarse aggregate particles which comprises priming the aggregate with afirst portion of a. surface active agent having at least one lipophilicradical per molecule, whereby the relatively fine aggregate particlesare preferentially primed, applying a bituminous hinder, whereby theprimed particles are coated with binder, applying a second portion of asurface active agent to the partially coated aggregate, whereby theuncoated relatively coarse aggregated particles are primed, and

mixing the entire composition, whereby the coarse and fine aggregateparticles become coated with the bituminous binder, said surface activeagent being applied in the form of an aqueous emulsion the total amountof said surface-active agent being between about 0.001% and about 0.1%by weight based on the aggregate.

17. The method of coating mineral aggregate containing both fine andcoarse aggregate particles which comprises priming the aggregate with afirst portion of a surface active agent having at least one lipophilicradical per molecule, whereby the relatively fine aggregate particlesare preferentially primed, applying a bituminous binder, whereby theprimed particles are coated with binder, applying a second portion of asurface active agent to the partially coated aggregate, whereby theuncoated relatively coarse aggregated particles are primed, and mixingthe entire composition, whereby the coarse and fine aggregate particlesbecome coated with the bituminous binder, said surface active agentbeing applied to the aggregate in the form of a dispersion the totalamount of said surface-active agent being between about 0.001% and about0.1% by weight based on the aggregate.

18. The method of coating mineral aggregate containing -60% by weight offine particles having maximum diameters between about 0.5 mm. and about5 mm. and coarse particles of greater diameter, which comprises primingthe aggregate with a first portion of a surface active agent agenthaving at least one lipophilic radical per molecule, whereby therelatively fine aggregate particles are preferentially primed, applyinga bituminous binder, whereby the primed particles are coated withbinder, applying a second portion of a surface active agent to thepartially coated aggregate, whereby the uncoated relatively coarseaggregated particles are primed, and mixing the entire composition,whereby the coarse and fine aggregate particles become coated with thebituminous binder, said first portion being from about 25% to about byweight of the total surface active agent the total amount of saidsurface-active agent being between about 0.001% and about 0.1% by weightbased on the aggregate.

19. The method of coating mineral aggregate containing both fine andcoarse aggregate particles which comprises priming the aggregate with afirst portion of a surface active agent having at least one lipophilicradical per molecule, whereby the relatively fine aggregate particlesare preferentially primed, applying a bituminous binder, whereby theprimed particles are coated with binder, applying a second portion of asurface active agent to the partially coated aggregate, whereby theuncoated relatively coarse aggregated particles are primed, and mixingthe entire composition, whereby the coarse and fine aggregate particlesbecome coated with the bituminous hinder the total amount of saidsurface-active agent being between about 0.001% and about 0.1% by weightbased on the aggregate.

References Cited in the file of this patent UNITED STATES PATENTS1,975,902 McConnaughay Oct. 9, 1934 2,003,861 McConnaughay June 4, 19352,025,945 Forrest Dec. 31, 1935 2,313,759 McCoy Mar. 16, 1943 2,339,853Hemmer Jan. 25, 1944 2,416,134 Allen Feb. 18, 1947 2,430,546 Agnew Nov.11, 1947 2,438,318 Johnson Mar. 23, 1948 2,461,971 Fischer Feb. 15, 19492,498,862 Petitjean Feb. 28, 1950

1. THE METHOD OF COATING MINERAL AGGREGATE CONTAINING BOTH FINE ANDCOARSE AGGREGATE PARTICLES WHICH COMPRISES PRIMING SAID AGGREGATE WITH AFIRST PORTION OF AN OIL-INWATER EMULSION, SAID EMULSION COMPRISING ANAQUEOUS PHASE HAVING DISSOLVED THEREIN FROM ABOUT 0.1% AND ABOUT 1% BYWEIGHT OF THE EMULSION OF A WATER SOLUBLE AMPHOTERIC METAL INORGANICSALT AND FROM ABOUT 1% TO ABOUT 6% BY WEIGHT BASED ON THE EMULSION OF AMINERAL ACID, AND A HYDROCARBON PHASE HAVING DISSOLVED THEREIN FROMABOUT 10% TO ABOUT 20% BASED ON THE WEIGHT OF THE EMULSION OF ANALIPHATIC AMINO COMPOUND BEARING AT LEAST ONE LIPOPHILIC RADICAL PERMOLECULE, WHEREBY THE FINE AGGREGATE PARTICLES HAVING MAXIMUM DIAMETERSLESS THAN ABOUT 5 MM. ARE COATED WITH THE PRIMER AND THE COARSERPARTICLES ARE SUBSTANTIALLY UNAFFECTED; MIXING WITH THE PRIMED AGGREGATEBETWEEN ABOUT 3% TO ABOUT 7% BY WEIGHT, BASED ON THE AGGREGATE, OF ABITUMINOUS BINDER, WHEREBY THE FINE AGGREGATE PARTICLES ARE COATEDTHEREWITH WHILE THE COARSER AGGREGATE PARTICLES ARE SUBSTANTIALLYUNCOATED; ADMIXING A SECOND PORTION OF SAID PRIMING EMULSION, WHEREBYTHE COARSE AGGREGATE PARTICLES ARE PRIMED THEREWITH; AND MIXING THEENTIRE COMPOSITION, WHEREBY BOTH FINE AND COARSE AGGREGATE PARTICLES ARECOATED WITH THE BINDER; THE TOTAL PROPORTION OF AMINO COMPOUND BEINGBETWEEN ABOUT 0.005% TO ABOUT 0.03% BASED ON THE WEIGHT OF THEAGGREGATE.